<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    var b = 5
    var test1 = function () {
      this.b = 11
    }
    var test = function() {
      return new Promise((resolve, reject) => {
        this.b = 88
        resolve(this.b)
      }).catch(err => {
        reject(err)
      })
    }
    test().then(res => {
      this.b = 99
    })
    test1();
    console.log(b)// 11
  </script>
</body>
</html>